Employee Benefit Plans - Components of Net Periodic Defined Benefit Cost (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Defined Benefit Pension Plans | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Interest cost | $ 2,376 | $ 2,538 | $ 2,161 |
| Expected return on plan assets | (3,353) | (3,409) | (3,975) |
| Amortization of actuarial (gain) loss | 1,340 | 934 | 1,238 |
| Total | 363 | 63 | (576) |
| OPEB | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Interest cost | 108 | 114 | 105 |
| Amortization of actuarial (gain) loss | (101) | (176) | (146) |
| Amortization of prior service credit | (621) | (644) | (688) |
| Total | $ (614) | $ (706) | $ (729) |